1. A loop at the end of a rope, tied with a knot so that it can be tightened and slackened, and used for trapping animals or hanging people.
2. A loop formed in a cord, or rope, by means of a slipknot; it binds tighter as the cord or rope is pulled.
3. Something that traps someone in an unpleasant or unwanted situation.
4. Etymology: from about 1450, from Old French nos or nous, "knot"; from Latin nodus, "knot".